Lower cementing plug



Aug. 15, 1939. 2. A. DYER LOWER CEIENTING PLUG Filed Dec. 22, 1937Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE Lowaa oamm'rmo PLUGApplication December 22, 1937, Serial No. 181,133

9 Claims;

This invention relates to the art of sinking deep wells, and hasparticular utility in the cementing off of casing installed in suchwells.

The cementing-off operation is generally accomplished by running acolumn of liquid cement down the casing preceeded by a lower" cementingplug and followed by'= an "upper" cementing plug. When the lower plugstrikes the cementing valve at the lower end of the casing, the lowerplug yields to permit the cement to pass by it, through the valve, anddownwardly into the lower end of the well from whence it flows upwardbetween the casing and the walls of the well.

After the charge of cement has hardened, a drill on a string of drillpipe is inserted into the casing and the cement plugs and cement valveare drilled out and the drilling operation continued downwardly todeepen the well.

Heretofore it has been the general practice to form the lower cementplugs of a single body of vulcanized rubber. These plugs were thusrelatively expensive, particularly in view of the fact they could onlybe used once and then were destroyed by the drill in deepening the well.

It is the object of my invention to provide a relatively inexpensivecementing plug for use in the cementing of deep wells.

In cementing operations hitherto it has been necessary to insert thelower cementing plug in the casing with a particular end thereofdisposed downwardly in order for this plug to allow the cement to beforced downwardly past the lower cementing plug after the latter hadcome into contact with the cementing valve plug at the bottom of thecasing. Due to carelessness these lower cementing plugs are sometimesinserted bottom side up with the result that it is not possible to forcethe cement downwardly out of the lower end of the casing and the entirecementing operation, therefore, fails.

It is another object of my invention to provide a lower cementing plugfor use in cementing deep wells which cannot be placed in the well tocause it to fail to perform its function satisfactorily.

The manner of accomplishing the foregoing objects as well as furtherobjects and advantages will be made apparent in the followingdescription taken in connection with the accompanying drawing in which-Fig. 1 is a fragmentary vertical sectional view of the bottom end of anoil well and illustrates a preferred embodiment of my invention beingused in a cementing operation for cementing the lower end of a string ofcasing in said well.

Fig. 2 is a 'view similar to Fig. 1 and illustrates a later step in saidcementing operation.

Fig. 3 is a plan view of the aforesaid preferred embodiment of myinvention.

Fig. 4 is a vertical sectional view taken on the line 4-4 of Fig. 3.

Fig. 5 is a perspective view of a separate flexible rubber washer whichis included as a part of the aforesaid preferred embodiment of myinvention.

Referring specifically to the drawing, I have shown in Figs. 1 and 2thereof a lower portion of an oil well in. Extending down the well i0 toa point near the bottom ll thereof is a casing l2 which has beeninserted into the well ill pre- Daratory to cement ng the lower end ofthis easing into the well. When the casing i2 was inserted in the wellit carried on the lower end thereof a float collar II, the interior ofwhich is provided with a cast iron plug it, having a back pressure valveit. After the casing i2 has been lowered, its lower end disposed as inFig. 1, the interior of the casing is filled with screened rotary mud ISon top of which a lower cementing plug comprising the preferredembodiment of my invention is inserted in the upper end ofthe casing. Amass of cement 2| is now introduced on'top of the plug 20, an upper plug22 is inserted in the casing above cement 2i and rotary mud 23 is pumpedinto the casing i2 to force the plugs 20 and 22, and the charge ofcement 2i disposed therebetween down through the casing l2.

The plug 20 includes a body which may be formed of molded rubber,Bakelite, wood or any other suitable material. The exterior surface iiof this body is substantially cylindrical and of a diameter which willpermit the plug to slide freely in the casing i2 with which it isdesigned to be used. Formed centrally in the outer cylindrical surface3| of the body 30 is an annular channel 32, having sloping faces 33 andan annular groove 34 which extends inwardly from the bottom 35 of saidchannel. The groove 24 is preferably formed on a plane which l es atright angles to the longitudinal axis of the body 30 and equidistantfrom the ends thereof.

Formed longitudinally in the outer surface 3| of the body 30 on eachside of the plane of the groove 34 is a series of passageways whichcommunicate between the channel 32 and the opposite ends of the plug. Ateach end of the plug there is preferably provided a central cavity 50with which all of the passageways 40 adjacent that end of the plugcommunicate. Thus producing a castellated head 52 on each end of theplug. While the plug of my invention may operate suitably with anynumber of passageways ll, I have found that it is preferable to havethree or more of these passageways, the reason for this being made clearhereinafter.

Lodged in the groove 34 so as to bisect the channel 32 is an annularwasher I, this washer having a slightly greater outside diameter thanthe inside of the casing i2, and having a central hold I which is ofsmaller diameter than that of the bottom of the groove ll. The washer Iis made of relatively flexible rubber and after its being molded isstretched and slipped over the end of the body II after which it isallowed to snap into the groove as shown in Figs. 3 and 4.

The plug of my invention is used in the normal manner of any lowercementing plug in the cementing into the well "of the casing l2. As theplug II, the body of cement 2| and the upper plug 22 move downwardthrough the casing ii, the plug 20 appears as shown in Fig. 1 Here it isseen that the washer lll is in substantially undistorted condition, theouter rim of this washer making a snug contact with the inner surface ofthe casing. The available space above the washer 60 in this view isfllled with the cement 2| while the available space below this washer isfilled with rotary mud i6.

When the cementing operation has proceeded to the point where the lowercastellated head 52 of the plug 20 has contact with the valve plug it,downward motion of the plug 20 ceases and the application of furtherpressure by the plug 22 downward on the cement 2i causes the latter todeflect the washer 60 downwardly as shown in Fig. 2. This deflectionpermits the cement 2i to flow past the washer 60, downwardly through thepassageways 40 and the cavity 50 of the lower castellated head 52 intothe valve plug H from which the cement passes through the valve II andout through the float collar i3.

Because the body 30 of the plug 20 of my invention is formed with acastellated head.52 on each of its opposite ends, this plug is certainto function properly when it reaches the lower end of the well no matterhow the plug is inserted in the top of the casing. Whichever castellatedhead 52 of the body 30 is pointed downwardly when it reaches the bottomend of the casing, this head 52 insures a ready flow of the cement 2|past the plug 20 and through valve plug M. It is thus seen that thefailure of a cementing operation by the improper placing of the lowerplug in the upper end of the casing is impossible when the lower plug 20of my invention is used.

What I claim is:

1. In a cementing plug for use in cementing casings in deep wells, thecombination of: a body having a reduced middle portion adapted toreceive an annular washer; an annular rubber washer mounted on saidportion; and guide heads formed on opposite ends of said body ofslightly less diameter than the outside diameter of said washer, therebeing longitudinal free fluid passages in said heads between the spacesadjacent opposite faces of said washer and opposite ends of said body.

2. In a cementing plug for use in cementing casings in deep wells, thecombination of: a body having a reduced middle portion adapted toreceive an annular washer; an annular rubber washer mounted on saidportion; and fluted guide heads formed on opposite ends of said body ofslightly less diameter than said washer.

3. In a cementing plug for use in cementing casings in deep wells, thecombination of: a body having a reduced middle portion adapted toreceive an annular washer; an annular rubber washer mounted on saidportion; and guide heads formed on opposite ends of said body ofslightly less diameter than the outside diameter of said washer, therebeing longitudinal tree fluid passages in said heads between the spacesadjacent opposite faces of said washer and opposite ends of said body,there being also relatively large central cavities formed in oppositeends of said body, said cavities communicating with said passages.

4. In a cementing plug for use in cementing casings in deep wells, thecombination of: a body having a reduced middle portion adapted toreceive an annular washer; an annular rubber washer mounted on saidportion; and fluted guide heads formed on opposite ends of said body ofslightly less diameter than said washer, there being relatively largecentral cavities formed in opposite ends of said body, said cavitiescommunicating with the flutes in said heads.

5. In a cementing plug for use in cementing casings in deep wells, thecombination of a substantially intgeral body having a reduced middleportion adapted to receive an annular washer; an annular rubber washermounted on said portion; and guide heads formed on opposite ends of saidbody of slightly less diameter than the outside diameter of said washer,there being longitudinal free fluid passages in said heads between thespaces adjacent opposite faces of said washer and opposite ends of saidbody.

6. A bottom cementing plug of the type described comprising a memberhaving enlarged end portions, having a reduced middle portion, having anannular flexible wiper extending outwardly from said reduced portion,and having fluid passageways extending from each end to the reducedportion but short of the wiper.

7. A cementing plug of the type described comprising a member havingenlarged fluted end por tions, having a reduced middle portion, andhaving an annular flexible wiper extending outwardly from said reducedportion.

8. A cementing plug of the type described comprising a substantiallycylindrical solid body portion having formed thereon at each endsegmental end portions with curved outer surfaces, the curved outersurfaces forming an enlarged interrupted cylindrical surface, said bodyportion and said segmental end portions defining a cup-like recess ateach end of the plug and defining radially disposed groovescommunicating therewith and adapted to act as fluid passageways, theinner end portions of said segmental end portions being inwardlytapered, and a flexible wiper encircling the middle of said body portionand extending beyond the outer diameter of the end portions 01' theplug.

9. A cementing plug of the type described comprising a member of arubber composition having enlarged fluted end portions, having a reducedmiddle portion, and having an annular flexible wiper extending outwardlyfrom said reduced portion.

ZEB A. DYER.

